Abrasive jet systems are used in precision cutting, shaping, carving, and other material-processing applications. During operation, abrasive jet systems typically direct a high-speed jet of water toward a workpiece to rapidly erode portions of the workpiece. Abrasive particles are added to the water to increase the rate of erosion. When compared to other material-processing or cutting systems (e.g., grinding systems, plasma-cutting systems, etc.), abrasive jet systems can have significant advantages. For example, abrasive jet systems often produce relatively fine and clean cuts, typically without heat-affected zones around the cuts. Abrasive-jet systems also tend to be highly versatile with respect to the material type of the workpiece. The range of materials that can be processed using abrasive jet systems includes very soft materials (e.g., rubber, foam, leather, and paper) as well as very hard materials (e.g., stone, ceramic, and hardened metal). Furthermore, in many cases abrasive-jet systems can execute demanding material-processing operations while generating little or no dust or smoke.
In a typical abrasive-jet system, a pump pressurizes water or another suitable fluid to a high pressure (e.g., 40,000 psi to 100,000 psi or more). Some of this pressurized fluid is routed through a cutting head that includes an orifice plate having an orifice. Passing through the orifice converts static pressure of the fluid into kinetic energy, which causes the fluid to exit the cutting head as a jet at high speed (e.g., up to 2,500 feet-per-second or more) and impact a workpiece. The orifice plate can be a hard jewel (e.g., a synthetic sapphire, ruby, or diamond) held in a suitable mount. In many cases, a jig supports the workpiece. The jig, the cutting head, or both can be movable under computer or robotic control such that complex processing instructions can be executed automatically.
Some conventional abrasive jet systems mix abrasive particles and fluid to form slurry before forming the slurry into a jet. This approach simplifies achieving consistent and reliable abrasive content in the jet, but can cause excessive wear on internal system components as the slurry is pressurized and then formed into the jet. In an alternative approach, abrasive particles are entrained in a fluid after the fluid is formed into a jet (e.g., after the fluid passes through an orifice of an orifice plate). In this approach, the Venturi effect associated with the jet can draw abrasive particles into a mixing chamber along a flow path of the jet. When executed properly, this manner of incorporating particles into a jet can be at least partially self-metering. For example, the replenishment of particles in the mixing chamber can automatically match particle consumption. The equilibrium between particle replenishment and consumption, however, can be sensitive to variations in the particle source upstream from the mixing chamber. In some applications, a large hopper with a direct gravity connection to a mixing chamber is ill-suited for consistent and reliable particle delivery. Large agglomerations of particles can be subject to clumping, rat holes, and other phenomena that can cause variability in and/or degradation of particle flow characteristics. These phenomena are often related to friction between the particles and, therefore, can be dependent on particle size. For example, many forms of undesirable particle behavior can be exacerbated by agglomerations of smaller particles to a greater degree than by agglomerations of larger particles.
In the context of abrasive jet systems, it can be useful to deliver abrasive particles to a cutting head in a consistent, reliable, and cost-effective manner. It can also be useful to enhance coordination between the delivery of abrasive particles and operation of other system components. For these and/or other reasons, there is a need for further innovation in this field.